Hi Michael, If you are working with metadata and timestamps, I think the gr-analysis module may be of use to you. As for your particular question, my understanding is that the 1PPS provides the timestamp information present in the metadata. So I would suppose the (possibly interpolated) sample with integer seconds would be on the PPS. But I’m not 100% confident on that so perhaps someone else can chime in and help us out. I will also point out the file metadata sink is not particularly efficient at writing metadata (although quite robust) so you may need something like specrec (in gr-analysis) for higher sample rates.
https://github.com/garverp/gr-analysis <https://github.com/garverp/gr-analysis> PWG > > From: Michael Skaggs <mskag...@umbc.edu> > Subject: [Discuss-gnuradio] 1PPS Synchronization - File Meta Sink Data > Date: April 1, 2016 at 10:49:30 AM EDT > To: discuss-gnuradio@gnu.org > > > Hi all, > > I'm doing a simple RF recording with a B200mini synchronized to an accurate > GPS 1PPS. I'm attempting to determine which samples(most importantly the > first one) fall on a 1PPS pulse. I'm using the File Meta Sink block in GRC to > try and extract information from the recording. When I read the data from the > header, here is what is shown: > > fileName: 'X:\XXXXX.dat' > ifileName: 'X:\XXXXX.idx' > ioType: 'r' > totalPulseCount: 11 > sampleCount: 1000000 > startTime: [0 0.1120] > timestamp0: '1970-01-01 00:00:00.112' > rx_rate: 1000000 > rx_time: [0 0.1120] > timestamp: '1970-01-01 00:00:00.112' > rx_freq: 500000000 > sampleType: 'float' > typeFlag: 'double' > vBit: 1 > impediance: 50 > samples: [] > > So, this is a 1 MSps recording with a center frequency at 500MHz and about 11 > seconds in length, so the extracted information is definitely correct. But a > couple of questions from the metadata: > > The "startTime" value is 0.1120. I realize that this is the time stamp of the > first sample of the segment. However, does that mean that sample 112000 > (1MSps*0.1120) is the first sample that falls on a PPS since the B200mini is > synced to it? > > Second, the "samples" field is empty. I was attempting to populate it with > sample numbers that fall on a 1PPS or a header. If the header is synchronized > to the 1PPS, this will be fairly easy. If not, is there a way to determine > which samples fall on the PPS? > > Thanks, > Michael > > > >
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